Considering that my sister is flying back from EZE next week on AA, I recently wondered why it's an overnight flight to South American cities like EZE and then have the plane sit there all day for it to be towed back to the gate for an overnight flight back to the US. Would the airlines save money by repositioning the flight times to have it leave an airport like ATL in the morning and then have it fly back in the night?

All airlines do this. From South America (at least from the southern cone) and Europe also. Reason is you don't lose a day sitting on the aircraft, and business travelers (high-yielding pax) pick these overnight flights over daylight ones.

Some airlines offer tag-on flights to improve aircraft use, others just wait all day long.

Business travelers demand overnight flights, so that is what they get. There are a handful of daylight services, mainly between Miami and Brazil, but that is it.

American Airlines used to only park one plane in Sao Paulo, with the other planes going to Belo Horizonte, a daylight to Miami, Rio de Janeiro, and Asuncion, though now they no longer do the Belo Horizonte and Asuncion tags.

LAN hates parking planes on the ground all day, so their flights to Miami often turn around and do a daylight flight to somewhere else depending on the day. For example, on Mondays, they have a daylight MIA-CCS-SCL service; on Saturdays LAN Chile has a daylight MIA-PUJ-SCL and LAN Argentina has a daylight MIA-PUJ-EZE.

I just wanted to add that you can see that just about the only long flights that operate during the day are one traveling west and only because the time changes allow it. Like many have said one a 10 hour flight going north south or east it takes that long or even longer times and business travelers can only aford to loose that time at night.

One mile of highway gets you one mile, one mile of runway gets you anywhere.

understandable. I really asking me how an airline can make money with a airplane all the day on the ground... for example the QF flight to FRA, the plane comes in at 04:55 am and leaves FRA again at 23:55

Deep South America flights to the US generally do the overnight and all day idle, although AA and DL have from time to time had daytime flights from GRU. Here are some reasons why this makes sense (and I just returned from Brazil today!):

-Connections beyond key points of GRU/GIG/SCL/EZE.... If the end destination is beyond any of these points (and in my example it was - SSA), you realistically can work a full day or at least a 3/4 day and then fly from end point to key point to return to the US that night. As for the arrivals from US to South America, this works a lot like Europe as you arrive in the morning, and can make connections or go to directly to the arriving city.

-Because the time difference between most of South America and the US is very small, an overnight flight to or from South America is easier to take than an overnight flight to Europe assuming you get some amount of rest on the plane (and I did last night on DL 104 GRU-ATL in Y, and I'm still up now and not tired - 10:29 P.M.).

-As do US travelers to South America, travelers from South America have likely more connection opportunities than a daylight flight would give to clear US customs and connect onward domestically or internationally. In fact, many people on my ATL-GRU flight were going onward to ICN and NRT. The flight attendants also gave the in-flight service announcements in English, Portugese, and Japanese. For DL, usually it is only English and destination country's principle language. Lastly, in GRU airport near gate 12, there is a large DL advertisement to go to Japan! A little further on this topic, you find that a lot of South American travelers shop almost exclusively by price (as do Americans!) and they sometimes make what may seem as bizarre routes because it is less expensive. For example - I flew ATL-CCS once next to a gentleman who flew PTY-ATL-CCS because Copa was like $1900 for the flight and DL was like $800 or something silly like that. So you may see people doing routes like GRU-ATL-MEX simply because the price makes it worth the US customs process and extra time. You may even see more of this with AA.

Now the one thing I don't know is the crew turn rules - if for example, a DL crew flies JFK-GRU and arrives at 8:00 in the morning - can they fly GRU-ATL at 10:55 that evening? That is 14:55 between landing and takeoff - and that may work good for crew reasons - no 'dead crews'.

Quoting Avianca (Reply 8):understandable. I really asking me how an airline can make money with a airplane all the day on the ground... for example the QF flight to FRA, the plane comes in at 04:55 am and leaves FRA again at 23:55

If you think that's bad, El Al used to have a plane arrive in Miami from Tel Aviv on Friday mornings, and it did not leave until midnight on Saturday. Almost two whole days, but it is because El Al does not fly on the Sabbath. They changed their schedule recently so the planes just turn around, though.

Quoting MAH4546 (Reply 10):If you think that's bad, El Al used to have a plane arrive.......

That is a good example, did El Al have any other stations with that type of idle configuration? Maybe in Asia, it was probably fairly common in that situation. Also, about crew, they may have had a stranded crew or had to dead head back in some scenarios.

Quoting MAH4546 (Reply 10):If you think that's bad, El Al used to have a plane arrive in Miami from Tel Aviv on Friday mornings, and it did not leave until midnight on Saturday. Almost two whole days, but it is because El Al does not fly on the Sabbath. They changed their schedule recently so the planes just turn around, though.

thats explain why EL AL has "so much" profit at the end of the year....

Quoting B4REAL (Reply 9):Connections beyond key points of GRU/GIG/SCL/EZE.... If the end destination is beyond any of these points ///// As for the arrivals from US to South America, this works a lot like Europe as you arrive in the morning, and can make connections or go to directly to the arriving city.

I think this is the REAL reason....connections on both ends. Business travelers don't LIKE to travel at night. We just HAVE to. Flights leave from the US in the evening so that people can get to NY or MIA or DFW from other parts of the country during the day in order to catch the flight to South America.

Let's look at what would happen if they had 'normal' turnaround times in South America. For purposes of this exercise, we'll use the times of the year when neither country is on daylight savings (just to keep the math simpler) and examine DL 146 and 147, the ATL-SCL-ATL service.

DL 147, as scheduled now

Depart ATL: 10:05 PM
Arrive SCL: 8:30 AM (this is a very convenient time for business travellers and tourists alike, btw, as you can easily be out of the airport by 10 and have almost a full day to do what you want.

Let's assume a 2 hour turn, so we have

DL 146 (hypothetically scheduled)

Depart SCL 10:30 AM
Arrive 9:25 PM

Take 90 minutes or so to clear customs, and you are basically unable to connect to anywhere. But DL **COULD** fix this problem. Let's try another schedule

DL 147

Depart ATL 7:05 PM
Arrive SCL 5:30 AM The 5:30 arrival is moderately inconvenient, but most connections from the west coast, even from smaller markets like SMF, are still possible, as are connections from Asia, which are actually better under this schedule.

Then, we have

DL 146

Depart SCL 7:30 AM
Arrive ATL 6:25 PM

This looks better on paper, but the reality is we haven't solved much in terms of connections. Most Europe flights are gone long before 8:00, as are the Asia flights. And while domestic connectivity is improved, a lot of folks would have to take the last flight of the day, not exactly ideal if something goes awry. So by trying this schedule, DL loses a lot of connecting possibilities (the whole reason the flight works in the first place), and this doesn't take into account the preference of high-yield passengers to travel with certain schedules.

Quoting MPDPilot (Reply 7):I just wanted to add that you can see that just about the only long flights that operate during the day are one traveling west and only because the time changes allow it.

Not really, on top of GRU-MIA and GRU-JFK daytime flights, JJ also operates MIA-GRU and JFK-GRU daylights. It has to do with plane utilization. This way JJ is able to have two flights a day to JFK and MIA with only two planes for each route, and offers both night flights and daytime flights both directions.

Presume the strategy is similar to AC, whereby flight timings are scheduled to capture large numbers of Asia > South America bound traffic and vice versa. This is a large (and growing) important market.

Given the limited number of flights to/from the US/Deep South America operated by non-US carriers, there is a lot of cargo hauled on the AA, UA, DL, and CO flights in these markets. This more than makes up for the lost revenue of having the aircraft parked for 10 hours at GRU, EZE, SCL, and so forth.

Some carriers also use the layovers to do maintenance and clean the aircraft.

Might not have any bearing to today (with the discussion above), but from the 1950s through to the 70s the real money was made by Pan Am, Braniff, Aero Peru, Avianca, Lan Chile, etc. on mail contracts. At Miami and the South American cities, those planes that flew at or near midnight got the sacks of mail that had been collected during the day. These were the money makers for the flights, because passenger loads varied so widely from day to day and week to week. Mail did not; it was high volume and even, and paid hard currency. So, for those decades, the passenger flew at the convenience of the mail volume. So, one surmise might be that what we see today is lingering from that original scheduling behavior.

Quoting Rafabozzolla (Reply 19):Not really, on top of GRU-MIA and GRU-JFK daytime flights, JJ also operates MIA-GRU and JFK-GRU daylights. It has to do with plane utilization. This way JJ is able to have two flights a day to JFK and MIA with only two planes for each route, and offers both night flights and daytime flights both directions.

I was refering to the whole planet. Yes there are a few day time flights but the vast majority of the day time flights are westbound.

One mile of highway gets you one mile, one mile of runway gets you anywhere.